The thread tension device on a sewing machine is intended to apply a prescribed amount of "drag" on the sewing thread to enable the sewing machine to properly set a stitch. Depending upon the type and thickness of the material being sewn, as well as the type and thickness of the thread, the drag, or tension setting, is varied such that an optimum stitch may be obtained. Ordinarily, thread tension devices use a spring for applying a compressive force to a set of tension discs between which the thread is passed. A screw arrangement is used to vary the compression on the spring thereby varying the tension on the thread. If the thread passing between the discs is uniform, this arrangement will supply a constant uniform tension to the thread. However, in actuality, the thread is not uniform and there are variations in the thickness thereof. This causes the tension discs to separate increasing the compression on the spring which, in turn, exerts a greater compressive force on the thread. This varying tension may result in improperly set stitches and even possible breakage of the thread itself.